Abstract: A mail transmission method includes: performing, by the first node, a fragmentation process on the mail data to obtain a plurality of data fragments; and for each data fragment, based on historically transmitted mail data, determining, by the first node, whether the data fragment is a data fragment that has been previously transmitted, when the data fragment is a data fragment that has not been previously transmitted, transmitting, by the first node, the data fragment to the second node, and when the data fragment is a data fragment that has been previously transmitted, transmitting, by the first node, a feature value of the data fragment to the second node, where the feature value is used to instruct the second node to acquire the data fragment.